JP2015533990A - Parts made of ceramic material with base and wall - Google Patents

Abstract

The present invention comprises a part forming a base (11) and a part forming a wall (13), the base (11) being made of a low porosity ceramic material, and the wall (13) being a sintered powder. Characterized in that it has a jacket (13E) and a core (13N), the core is located in the jacket, and the porosity of the core is larger than the multi-efficiency of the base and increases with increasing distance from the base. The present invention relates to a component (10) made of a ceramic material.

Description

  The present invention relates to the field of manufacturing components made at least in part of ceramic materials, and more particularly to components for turbine engines, particularly gas turbine engines such as turbine rotor blades or fixed nozzle vanes.

  High-temperature components in turbine engines where high-temperature gas flows use alloys capable of withstanding such temperature levels and, if necessary, fluids that allow these components to operate at temperatures beyond the stability of the material. Proper cooling using

  In connection with the development of new gas turbine engines in the aviation field, there is a need for lighter materials with good structural properties even at high temperatures. Ceramics are materials that meet these requirements. Ceramics are used for components located in the rear of the engine from the turbine downstream from the combustion chamber.

  The powder sintering manufacturing technique is a conventional technique, in which mechanical parts and others are made directly from somewhat finer powder. According to a certain manufacturing method, the powder is agglomerated through various processes to form a semi-finished part. The component is heated to a temperature sufficient for the particles to melt or bond together by diffusion along the contact area. In this way, parts are coupled to a given level. According to one particular technique, the part is made from successive layers. In this method, the material is in powder form and is heated under the action of a laser beam or electron beam directed along a path corresponding to the surface of a part of the part. By repeating the step of attaching the powder and sintering the powder using a laser or an electron beam, the part gradually increases in thickness and a desired shape can be obtained. The amount of heat applied by the laser beam or electron beam depends on the nature of the material. If necessary, a heat-sensitive polymer (with or without preceramics) can be used to ensure bonding during part formation. The polymer can also be removed by heat treatment. FIG. 2 is an illustration of an apparatus for producing parts by laser heating, and details of the implementation of this technique are described below.

  In view of the higher temperature limits of ceramics for high temperature parts of gas turbine engines than the alloys used in the prior art, Applicants are based on the technology of combining powders using laser beams or electron beams. The purpose is to produce parts such as turbine rotor blades from ceramic materials.

  Another object of the present invention is to provide means for reducing the mechanical stress at the root portion of a rotating component such as a turbine rotor blade to such an extent that the maximum mechanical stress remains at the root portion.

  Another aspect of the present invention is a means of reducing the likelihood of critical size defects occurring because strain in parts made of monolithic ceramic materials is caused by defects.

  Yet another object of the present invention is the design of components that can be cooled, since the temperature at which they are likely to be exposed may exceed the use limit temperature of the ceramic.

  Since cooling can be ensured by the circulation of fluid in the part and intended to create a flow path in the part for this purpose, yet another object of the present invention is such a flow path during the production of the part. Is a method of forming ceramics so that can be made.

  In particular, this method does not require the use of extensive machining techniques.

  According to the invention, these objects are achieved by a part made of a ceramic material. This part consists of a part forming a base and a part forming a wall, the base being made from a low-porosity ceramic material and the wall being obtained by sintering ceramic powder. The wall further has a jacket or shell and a core, the core being located in the jacket, wherein the porosity of the core is greater than the porosity of the base and increases with increasing distance from the base.

  By having a porosity or density gradient, the structure of the part according to the invention can have a fairly light part, which ensures a reduced stress level on the base if it is a moving part. The Furthermore, thanks to the reduced amount of ceramics in the part, there is the advantage of reducing the possibility of the occurrence of critical size defects that can weaken the structure.

  Furthermore, unlike the prior art, the presence of porosity and cavities allows circulation of the cooling fluid without the need for machining.

  Preferably, the base is also made by powder sintering of ceramics.

  According to another characteristic, the porosity of the material forming the base is less than 3%, while the porosity of the core is greater than 5%, preferably between 10% and 50%.

  The term “porosity” relates to the proportion of voids in that part of the part. This void is related to the structure of the material and to the space created between the particles of ceramic material and constrained in the structure. The density of the material is inversely related to the porosity.

  In another embodiment of the present application, in the portion forming the wall, the relationship between the amount of cavities formed by the narrow partition walls formed by the bonded ceramic grains and the partition wall volume is also expressed in terms of porosity.

  In addition, if cooling is performed, the base also includes a flow path for carrying cooling air to the wall. In this case, the channel does not fall within the definition of base porosity.

  In the present application, the present invention has the following two aspects. Controlling the porosity and thus the density of the ceramics, and creating cavities in the part walls, resulting in a reduction in the amount of material.

  Thus, according to the first embodiment, the core consists of a porous material made of ceramic particles that are bonded by partial sintering and form voids therebetween.

  “Partial sintering” is understood to mean a technique of sintering at a temperature below that which would lead to maximum density.

  According to another embodiment, the core consists of cavities partitioned by partition walls, which are made by sintering using a laser beam or an electron beam. The partition walls are high in density and the porosity is less than 3%.

  Advantageously, the core has portions with different cavities, specifically a portion where the size of the cavities increases with increasing distance from the base.

  According to a particular embodiment, the part comprises a heel in the extension of the wall, the porosity of the heel being less than the porosity of the material forming the core.

  In particular, the invention relates to a turbine engine blade where the base forms the root of the blade, the wall forms the blade wing, and optionally has a heel with a porosity less than the porosity of the core.

  The invention also relates to a method of manufacturing such a part. The method includes the steps of forming a wall using a sintering tray containing powder that is flush with the base at the start of the step, and selectively sintering the powder into a continuous layer by a laser beam or electron beam. A continuous layer is obtained by progressively moving the part downward in the sintering tray.

  In particular, the method includes separately preparing the base by powder sintering and then depositing successive layers of ceramic powder and forming the walls by joining the successive layers by sintering the layers. .

  The invention will be better understood in the embodiments of the invention described in detail below through non-limiting examples purely by way of example with reference to the accompanying schematic drawings, and other objects and details of the invention. The features and benefits will also become clearer.

1 shows a turbine rotor blade made of a ceramic material having a structure according to the invention. FIG. It is a figure which shows a laser fusion sintering apparatus. FIG. 3 illustrates one base of a part according to the invention. It is a figure which shows the 1st layer formed by laser sintering on the base of FIG. It is a figure which shows the modification which has two turbine blades on the same base.

  Referring to FIG. 1, it can be seen that the turbine blade 10 forms a part that can be made in accordance with the present invention. The blade has a root or base 11 which is attached to the rim of the turbine disk. This root has a platform 12 mounted thereon, the root extending to a wall 13 forming a blade wing that sweeps hot engine gas in the direction of centrifugal force applied during engine operation along axis XX. Yes. In this case, the blade comprises a sealing strip 16 and has a heel 15 mounted on the blade. The heel 15 and the platform are elements of the outer and inner surfaces of the gas engine duct, respectively, with blade blades extending radially between them. The seal strip forms a seal with a ring disposed on the turbine stage stator.

  According to the invention, this part made of ceramic material changes in density along the axis XX. The density change is schematically shown in a cross section (parts A, B, C, D along the axis XX) along a plane orthogonal to the axis XX.

  The base 11 has a maximum density. This is, for example, an element obtained by molding ceramic powder in a mold, and the powder may be bound with a binder. This step is followed by a sintering heat treatment of the semi-finished product made with the mold. Depending on the composition of the material used, an intermediate treatment including a binder removal step may be performed. The porosity of this element is preferably less than 3%.

  The wall 13 has a jacket 13E and a core 13N. The jacket forms the outer surface of the wall. The jacket is thin, for example less than 1 mm, preferably approximately 0.5 mm, and has a low porosity like the base. The jacket defines a core 13N having a relatively high porosity. The porosity of the core is greater than 5%, preferably between 10% and 50%. Correspondingly, the density of the core is relatively small, providing the above advantages of reducing mechanical stress on the base due to centrifugal force when the part is mounted on the rotor as in this embodiment. Advantageously, the density is not the same throughout the axis. As can be seen in sections B and C, this density is schematically represented by different grid patterns that are relatively small or relatively large in the mesh. The heel indicated by the cross section D may be lower in density than the base or may be higher in density than the wall. This is made of sintered particles of ceramic powder.

  Such parts are partly made by powder sintering, the method of which will be described again below in connection with the apparatus of FIG. FIG. 2 shows an apparatus for producing parts by powder sintering using a laser beam or an electron beam.

  The laser beam or electron beam generator 1 emits a beam 2 having an appropriate output, the beam is directed to an array of reflectors 3, and the last mirror 4 of the reflector is a component to be fabricated, such as the blade 10 described above. Is pivoted to ensure that the surface is swept.

  The already formed parts P are buried in the tray 6 so that they are covered with a layer of powder 7 in a form suitable for sintering at regular intervals. A second tray 8 for feeding powder is placed beside the sintering tray 6 and filled with the sintered powder 7. In order to cover a part of the part P with a powder layer of a given thickness, the device forming the piston 9 can move a given amount of powder 7 from the supply tray 8 to the sintering tray 6. The thickness of this layer corresponds to the increased thickness of the part of the part during the sintering pass between the particles by the beam 2. By means of a device that lowers the sintering tray 6 and raises the supply tray 8, on the one hand the part P to be sintered is flush with the side of the tray 6 and on the other hand a layer of powder 7 with the correct thickness. Can be brought to face the piston 9 of the supply tray 8.

  Sintering and bonding of the particles forming the part 10 is performed in a continuous basic operation performed in the following manner. That is, since the part P is flush with the side of the sintering tray 6, the piston 9 moves toward the tray 6 and puts a powder 7 having a desired thickness on the part P. After the deposition, it returns to the standby position at the end of the supply tray 8. The laser beam or electron beam 2 uses the vibrating mirror 4 to sweep the surface of the part P, thereby causing partial melting of the surface part of the layer or promoting diffusion between the particles. A temperature rise is caused, and the layer is integrated with the component P to increase the thickness. The formed part P then moves downwards to offset the increase in thickness, so that the surface is flush with the sintering tray 6 again, while the supply tray 8 is raised. Thus, a sufficient amount of the powder 7 can be supplied facing the piston 9. By repeating this process as many times as necessary, the shape and dimensions required for the finished part 10 are reached.

  According to the invention, the base 11 of the part to be produced is first placed in the sintering tray 6. The base 11 shown in FIG. 3 is preferably obtained separately using a conventional ceramic powder sintering method. In the conventional ceramic powder sintering method, a semi-finished part made of ceramic powder and a binder is formed in a mold, and then a sintering heat treatment accompanied by an intermediate debinding process step is performed. In the case of a turbine rotor blade, the base 11 preferably comprises the blade root and may optionally comprise a platform. With the prior art sintering method, parts with very high density and porosity of less than 3% can be produced. According to a feature of the method of the present invention, the base 11 may be provided with a flat portion on the upper surface thereof and, if a platform is provided, on the platform portion.

  The base is disposed in the sintering tray together with the ceramic powder, and the flat portion thereof is flush with the surface of the powder. The method then includes making a wall 13 on this base 11 (FIG. 4) using a laser beam or electron beam according to the steps described above. The path of the beam is controlled by a control element that keeps the wall geometric features in memory. To create a layer, the beam is controlled not only in position but also in terms of energy input.

  Therefore, the surface of the jacket 13E is built into the layer with a given porosity, specifically less than 3% as with the base. Under this surface, the core 13N is made such that the porosity is greater than the porosity of the surface. When performing partial sintering, if the energy of the beam is maintained at a low level, a low density can be obtained. The porosity is greater than the base porosity. At least 5%, preferably between 10% and 50%. By manipulating the layer units to make the part, the layer can be made to be a core whose porosity varies along the axis XX. This porosity advantageously increases between the base and the heel.

  According to a modification of the wall core, the partition wall is formed by controlling the movement of the laser beam, and a cavity is formed between the partition walls so as to have a honeycomb structure. The partition wall is made of a material having a high density such as a surface forming an outer cover. The size of the cavity may be varied for convenience and preferably increases between the base of the blade and the heel.

Any kind of ceramic material may be used. Preferably, ceramics that can be used at temperatures exceeding 1000 ° C. are selected. For example, there are carbides such as SiC, oxides such as Al ₂ O ₃ , and nitrides such as Si ₃ N ₄ . Eutectic ceramics are also suitable.

  The particle size of the powder is selected so that it can be sintered using a laser beam or an electron beam. It has been observed that the smaller the size of the powder, the easier it is to make partial sintering at lower temperatures.

The laser beam or electron beam is adapted to the material to be processed. For example, in the case of alumina Al ₂ O ₃ , a YAG laser that emits a laser with a wavelength of 9400 cm ⁻¹ and has an output between 10 W and 30 W and an optimum movement of 96 mm / S is suitable for this application.

  The ceramic may form part of a mixture having a hot melt precursor that forms a binder, and may later be removed by a suitable heat treatment.

  If it is necessary to reduce the roughness, finishing may be incorporated.

  In the method used to manufacture these parts, a large residual stress is generated by the temperature gradient generated by continuously melting the layers. This temperature gradient may increase depending on the shape, thickness, and cross-sectional change of the part to be manufactured. Depending on the material, the residual stresses resulting from this temperature gradient can deform the part being manufactured and can cause cracks and cracks during use. Therefore, it is important to control the temperature in the sintering process and to keep the temperature of the powder uniform in order to minimize the residual stress during solidification. Any suitable heating means such as resistance heating means is used for this purpose.

  According to a variation of the present invention, the part is a pair of turbine blades as shown in FIG. Thus, using the solution provided by the present invention, it is possible to make two walls directly on the same base. The base 111 includes a root for mounting on a turbine disk and a platform 112. Two walls 113, 113 'correspond to two adjacent walls of the turbine rotor and are supported on this platform. The two walls are made in the same way as described above.

Claims (11)

  A part (10) made of a ceramic material, comprising a part forming a base (11) and a part forming a wall (13), the base (11) being made from a ceramic material having a low porosity. The wall (13) is obtained by sintering ceramic powder, the wall (13) further comprises a jacket (13E) and a core (13N), the core being located in the jacket, the porosity of the core The component (10), characterized in that is greater than the multi-efficiency of the base and increases with increasing distance from the base.   2. Part according to claim 1, wherein the base (11) is made by sintering ceramic powder.   3. Part according to claim 1 or 2, wherein the material forming the base (11) has a porosity of less than 3%.   4. Part according to any one of the preceding claims, wherein the porosity of the core (13N) is greater than 5%, preferably between 10% and 50%.   The component according to any one of claims 1 to 4, wherein the core (13N) is made of a porous material made of ceramic particles bonded by partial sintering.   The component according to any one of claims 1 to 3, wherein the core (13N) comprises a cavity partitioned by a partition wall, and a material forming the partition wall has a multi-efficiency of less than 3%.   7. Part according to any one of the preceding claims, wherein the core (13N) consists of parts with different cavities, in particular the size increases as it goes away from the base.   8. Part according to any one of the preceding claims, wherein the extension of the wall (13) comprises a heel (15), the porosity being smaller than the porosity of the material forming the core.   A component forming a turbine engine blade, wherein the base forms the root of the blade, the wall forms a blade wing, and optionally has a porosity heel that is less than the multi-efficiency of the core. The component according to any one of the items.   Forming a wall (13) using a sintering tray (6) containing powder that is flush with the base (11) at the start of the step, and selecting the powder into a continuous layer using a laser beam or electron beam Sintering step, wherein a continuous layer is obtained by progressively moving the part downward in the sintering tray (6). A method for manufacturing a part.   11. The method of claim 10, further comprising: separately producing a base by powder sintering; and subsequently depositing successive layers of ceramic powder and bonding the successive layers by sintering the layers. the method of.

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